Field
Aspects of the present disclosure relate generally to systems and methods for powering up circuits, and more particularly, to reducing the time to power up a circuit using a voltage comparator.
Background
A circuit (e.g., a CPU, a GPU, a processor core, etc.) may be selectively coupled to a power supply rail by an array of head switches. The head switches may decouple the circuit from the power supply rail when the circuit is in an inactive state (e.g., sleep state), and couple the circuit to the power supply rail when the circuit is in an active state (e.g., functional state). For example, the head switches may decouple the circuit from the power supply rail to reduce power leakage when the circuit is in the inactive state.
To power up a circuit from the inactive state to the active state, the head switches may be sequentially switched on (tuned on) by a power sequencer to ramp up the voltage of the circuit. Before power up, capacitors in the circuit may be fully discharged. As a result, during initial power up, the circuit may draw a large current from the power supply rail to charge the capacitors, creating a voltage droop on the power supply rail. If the power up is too fast, the voltage droop may be large enough to cause other circuits coupled to the power supply to malfunction. To prevent this, the power up may be slowed down by inserting delays between the head switches.